摘要
江西广丰早白垩世晚期碱性橄榄玄武岩中含有大、小两类单斜辉石斑晶,它们的主量元素间呈线性相关,且与大斑晶、小斑晶相平衡的岩浆Mg#值均类似于寄主岩石的Mg#值,说明它们与寄主岩石同源。早期的单斜辉石大斑晶粒径达1～1.5cm,SiO2,MgO,TFeO,CaO含量和Mg#值相对较低,Al2O3和TiO2含量相对较高,具有碱性玄武岩中单斜斑晶的矿物学特征;而晚期的单斜辉石小斑晶粒径为0.3～0.5cm,SiO2,MgO,TFeO,CaO含量和Mg#值相对较高,Al2O3和TiO2含量相对较低,也具有碱性玄武岩中斑晶的矿物学特征。单斜辉石大斑晶Wo(硅灰石)相对较高,En(顽辉石)含量相对较低,主要为含钛透辉石、含钛次透辉石,结晶温度为1272～1349℃、压力为1.23～1.93GPa,深度相当于41～64km,可能是原始岩浆绝热底辟上升结晶形成的;单斜辉石小斑晶Wo含量相对较低,En含量相对较高,主要为含钛普通辉石和顽透辉石,结晶温度为1186～1220℃、压力为0.44～0.75GPa,深度相当于15～25km,可能是相对原始的岩浆上升到浅部发生结晶分异作用形成的。
There are two types of clinopyroxenes phenocryst,the big one and the small one,in early cretaceous alkali olivine basalt from Guangfeng,Jiangxi Province. The linear correlation of their major elements and the similar Mg# of their balanced magma and the host rocks indicate that the big clinopyroxenes phenocryst,the small clinopyroxenes phenocryst and the host rocks are comagmatic. The diameter of the big clinopyroxenes phenocryst is 1 ～ 1. 5 cm,the small clinopyroxenes phenocryst is 0. 3 ～0. 5 cm. Both of them have the mineralogical characteristics of alkali basalt phenocryst,but Content of SiO2,MgO,TFeO,CaO,En（ Enstatite） and Mg# of the big clinopyroxenes phenocryst is lower than that of the small one,while the content of Al2O3,Wo（ Wollastonite） 和 TiO2 is higher. The crystallizing temperature and pressure of the big clinopyroxenes phenocryst respectivly is 1272 ～ 1 349 ℃ and 1. 23 ～1. 93 GPa,at depth of 41 ～64 km,while the small clinopyroxenes phenocryst is 1 186 ～ 1 220 ℃ and 0. 44 ～0. 75 GPa,at depth of 15 ～25 km. The big clinopyroxenes phenocryst probably are the crystallizing products formed by the primary magma in deeper magma chambers,while the small clinopyroxenes phenocryst probably are the fractional crystallizing products formed by the relativly primary magma in shallower magma chambers.
出处
《东华理工大学学报（自然科学版）》
CAS
2010年第2期120-130,共11页
Journal of East China University of Technology(Natural Science)
基金
中国核工业地质项目"中国中新生代铀成矿作用"
东华理工大学研究生创新基金资助(DYCA10019)
关键词
碱性橄榄玄武岩
单斜辉石
早白垩世
广丰
江西
Clinopyroxenes
Mineral chemistry
Alkali olivine basalt
Early Cretaceous
Guangfeng
